Light-emitting device

ABSTRACT

A light-emitting device includes a plurality of light-emitting elements, a plurality of light-transmissive members, and a covering member. The light-emitting elements each has a light-extracting surface. The light-emitting elements each includes a layered structure including a semiconductor layer, and a plurality of electrodes connected to the layered structure. The light-transmissive members each has a lower surface facing the light-extracting surface of at least one of the light-emitting elements, and an upper surface opposite to the lower surface and having an area smaller than an area of the lower surface. The upper surface of each of the light transmissive members collectively constitutes a light-emitting part having an outermost periphery with a square shape or a circular shape. The covering member integrally covers lateral surfaces of the light-emitting elements and lateral surfaces of the light-transmissive members.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2017-163346 filed on Aug. 28, 2017, the disclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present disclosure relates to a light-emitting device.

2. Description of Related Art

Various light sources have been used for electronic apparatus and the like. Light source devices employing light-emitting diodes in which light-emitting elements and wavelength conversion substances are combined have been used in recent years. In the case where such light source devices are used for some applications such as light sources of flashes for cameras, colors of light emitted from a plurality of light source devices are mixed to reproduce white light, and there is a demand that the light source devices have uniform and high luminance (for example, see U.S. Pat. No. 8,163,580).

SUMMARY OF THE INVENTION

In the case where a plurality of light-emitting devices are arranged, certain intervals between the light-emitting devices are required in order to ensure precision in mounting, so that a region between the light-emitting devices may not have a sufficient luminance, and unevenness in luminance may occur.

The present invention has been made in view of problems as described above, and one object thereof is to provide a light-emitting device that can achieve improvement in luminance and reduction in unevenness in luminance.

According to one embodiment of the present invention, a light-emitting device includes a plurality of light-emitting elements, a plurality of light-transmissive members, and a covering member. The light-emitting elements each has a light-extracting surface. The light-emitting elements each includes a layered structure including a semiconductor layer, and a plurality of electrodes connected to the layered structure. The light-transmissive members each has a lower surface facing the light-extracting surface of at least one of the light-emitting elements, and an upper surface opposite to the lower surface and having an area smaller than an area of the lower surface. The upper surface of each of the light transmissive members collectively constitutes a light-emitting part having an outermost periphery with a square shape or a circular shape. The covering member integrally covers lateral surfaces of the light-emitting elements and lateral surfaces of the light-transmissive members.

The light-emitting device according to the above described embodiment can achieve improvement in luminance and reduction in unevenness in luminance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic top plan view of a light-emitting device according to a first embodiment.

FIG. 1B is a schematic cross-sectional view taken along a line A-A′ in FIG. 1A.

FIG. 1C is a schematic bottom plan view of the light-emitting device according to the first embodiment.

FIG. 1D is a schematic perspective view of the light-emitting device according to the first embodiment when viewed from above.

FIG. 1E is a schematic perspective view of the light-emitting device according to the first embodiment when viewed from below.

FIG. 2A is a schematic top plan view of a light-emitting device according to a second embodiment.

FIG. 2B is a schematic cross-sectional view taken along a line B-B′ in FIG. 2A.

FIG. 3 is a schematic top plan view of a light-emitting device according to a third embodiment.

FIG. 4A is an illustrative schematic bottom plan view of a light-emitting device according to one embodiment.

FIG. 4B is an illustrative schematic bottom plan view of a light-emitting device according to another embodiment.

FIG. 5A is an illustrative schematic cross-sectional view of a light-transmissive member employed for a light-emitting device according to one embodiment.

FIG. 5B is an illustrative schematic cross-sectional view of a light-transmissive member employed in a light-emitting device according to another embodiment.

FIG. 5C is an illustrative schematic cress-sectional view of a light-transmissive member employed for a light-emitting device according to even another embodiment.

FIG. 5D is an illustrative schematic cross-sectional view of a light-transmissive member employed for a light-emitting device according to still another embodiment.

FIG. 6 is a schematic cross-sectional view of showing an example when the light-emitting device according to the first embodiment is mounted on a mounting board.

DETAILED DESCRIPTION OF EMBODIMENTS

The following describes embodiments of the present invention in detail with reference to the accompanying drawings. The descriptions below include terms (such as “up”, “down”, “right”, “left”, and other terms inclusive of these terms) indicating specific directions or positions as appropriate. These terms are used to facilitate understanding of the invention with reference to the drawings, and these terms do not limit the technical scope of the present invention. Portions indicated by the same reference numeral in different drawings represent the same portion or member.

As shown in, for example, FIGS. 1A to 1E, a light-emitting device 10 according to certain embodiments of the present invention includes light-emitting elements 11, light-transmissive members 12, and a covering member 13.

In particular, in the light-emitting device 10, upper surfaces 12 a of the light-transmissive members 12 constitutes a light-emitting portion, and the perimeter (i.e., the dotted line in FIG. 1A indicated by X1) of the light-emitting portion forms a square shape or a circular shape.

With this structure of the light-emitting device including a plurality of light-emitting elements, unevenness in luminance due to gaps between the light-emitting elements can be effectively prevented, and luminance can be improved. Further, the external appearance or look of the light-emitting device viewed from the light-extracting surface can be also improved.

Light-Emitting Elements 11

For example, semiconductor light-emitting elements such as light-emitting diodes can he used for the light-emitting elements 11. Each of the light-emitting elements includes a layered structure including a semiconductor layer. The layered structure may include a sapphire substrate or a light-transmissive growth substrate made of a semiconductor material (such as a nitride semiconductor material) that transmits light emitted from the layered structure, or the growth substrate may be removed from the layered structure to expose the semiconductor layer. The layered structure includes a plurality of semiconductor layers such as an n-type semiconductor layer a light-emitting layer (i.e., active layer), and a p-type semiconductor layer. Examples of the material for the semiconductor layers include semiconductor materials such as group III-V compound semiconductors and group II-VI compound semiconductors. More specifically, a nitride semiconductor material such as In_(X)Al_(Y)Ga_(1-X-Y)N (0≤X, 0≤Y, X+Y≤1) can be used.

The light-emitting element 11 includes a plurality of electrodes 11 a and 11 b connected to the layered structure. The plurality of electrodes 11 a and 11 b are preferably connected to the same surface of the layered structure but may be connected to different surfaces. Each of the plurality of electrodes 11 a and 11 b may have a single-layer structure or a layered structure as long as the electrodes have ohmic contact with the layered structure so that their current-voltage characteristics are linear or substantially linear. Such electrodes can be made of a material and can have a structure known in the field of the invention with any appropriate thickness. For example, the thickness of the electrodes is preferably a dozen to three hundred micrometers. For the electrodes, a good electrical conductor, preferably a metal such as Cu, can be used. The shape of the electrodes can be selected from various shapes in accordance with the purpose and the intended use. The plurality of electrodes of the light-emitting element may have the same shape or different shapes.

In the case where the plurality of electrodes are disposed on the same surface of the layered structure, the surface of the layered structure on which the electrodes are not disposed serves as the upper surface of the light-emitting element, and the surface of the layered structure on which the electrodes are disposed serves as the lower surface. The upper surface of the light-emitting element serves as the light-extracting surface.

In the case where a plurality of light-emitting elements 11 are arranged in the light-emitting device, such as the case where four light-emitting elements 11 are arranged, the light-emitting elements 11 may be arranged in two rows and two columns as shown in FIGS. 1A, 2A and 3. In the case where the light-emitting elements 11 are arranged in two rows and two columns, examples of arrangements of the electrodes 11 a and 11 b include: an arrangement in which the electrodes 11 a and 11 b extend along the column direction with the electrodes of the same polarity being aligned along the column direction, while the two columns have opposite polarity arrangements as shown in FIG. 1C; an arrangement in which the electrodes 11 a and 11 b extend along the column direction with the electrodes of the same polarity being aligned along the column direction, while the two columns have the same polarity arrangement so that the electrodes having different polarities are alternately aligned along the row direction as shown in FIG. 4A; and an arrangement in which the pairs of electrodes 11 a and 11 b of adjacent ones of the light-omitting elements 11 in respective row or column are rotated by 90° in the a single direction as shown in FIG. 4B.

The wavelengths of the light-emitting elements can be appropriately selected in accordance with characteristics of the light-emitting device to be obtained. For example, the wavelengths of the light-emitting elements can be in a range of 400 nm to 700 nm. A single light-emitting device may include two or three light-emitting elements, preferably includes four or more light-emitting elements, and may include six light-emitting elements. Among these cases, the number of light-emitting elements is preferably even, and is more preferably four or six.

The light-emitting elements 11 can have various shapes in a top view such as circles, ellipses, or polygons such as quadrilaterals or hexagons. The light-emitting elements 11 preferably has a quadrilateral shape in a top view, and more preferably has a square shape or a substantially square shape. In the specification of the present application, the expression “substantially square” refers to a quadrilateral shape in which difference between lengths of long sides and short sides is in a range of approximately ±10%. In a single light-emitting device, a plurality of light-emitting elements are preferably arranged such that the outermost periphery of the light-emitting elements has a quadrilateral shape, more preferably a square shape or a substantially square shape. For example, it is preferable that two light-emitting elements 11 having a rectangular shape in a plan view be aligned in the short-side direction. In the case where four light-emitting elements 11 having a square shape in a plan view are used, two light-emitting elements 11 are preferably aligned in each of the longitudinal and lateral directions. These arrangements allows for improving the external appearance of the light-emitting device when viewed from the light-extracting surface.

Light-Transmissive Members 12

The light-transmissive members 12 are disposed on the light-extracting surfaces of the light-emitting elements and transmit light emitted from the light-emitting elements to allow the light to be emitted to the outside. The light-transmissive members 12 preferably cover at least the entirety of the light-extracting surfaces of the light-emitting elements. For example, each of the light-transmissive members 12 preferably has the same size as the light-extracting surface of a corresponding one of light-emitting element, but variations in size of approximately ±10% are acceptable.

An outermost shape of the light-transmissive member 12 can have various shapes in a plan view such as a circular shape, an ellipse shape, and a polygonal shape such as a quadrilateral shape. Among these shapes, a square shape or a substantially square shape is preferable. This structure allows for improving the external appearance of the light-emitting device when viewed from the light-extracting surface, in particular, the external appearance of the plurality of light-transmissive members described below.

Each of the light-transmissive members 12 has a lower surface 12 b facing the light-extracting surface of at least one of the light-emitting elements, and the upper surface 12 a opposite to the lower surface 12 b.

The upper surface 12 a of each of the light-transmissive members 12 preferably has an area smaller than an area of the lower surface 12 b. For example, each of the light-transmissive members 12 may have lateral surfaces inclined toward the inner side of the light-transmissive member 12 along the direction toward the upper surface 12 a, or may have stepped lateral surfaces with a shape similar to a shape of a stack of two members. In other words, the light-transmissive member 12 preferably has projecting portions Z laterally protruding from the lateral surfaces as shown in FIG. 5A and other drawings. Each of the projecting portions Z preferably has a lower surface, a surface perpendicular to or inclined with respect to the lower surface and in contact with the lower surface, and a surface in contact with the surface perpendicular to or inclined with respect to the lower surface and being parallel to the upper surface 12 a of the light-transmissive member 12. The lower surface of each projecting portion Z in this case is preferably in the same plane with the lower surface 12 b of the light-transmissive member 12. In particular, it is preferable that the lateral surfaces has the projecting portions. The projecting portions may be disposed on the entirety of lateral surfaces of the light-transmissive member 12 or may be disposed only on some of the lateral surfaces.

The difference between an area of the upper surface 12 a and an area of the lower surface 12 b is preferably such that, for example, the area of the upper surface 12 a is 98% or less, more preferably 95% or less, further preferably 93% or less, of the area of the lower surface 12 b. Also, the area of the upper surface 12 a is preferably 80% or more, more preferably 82% or more, and further more preferably 85% or more of the lower surface 12 b. In particular, at least a part of a periphery of the upper surface 12 a of the light-transmissive member 12 preferably coincides with at least a part of a periphery of the light-emitting element 11 in a plan view. This structure allows for improving the light extraction efficiency. Meanwhile, at least a part of the periphery of the lower surface 12 b of the light-transmissive member 12 may coincide with at least a part of the periphery of the light-emitting element 11 in a plan view. This structure allows for reducing leakage of light and further improving the light extraction efficiency through the upper surface 12 a, so that the luminance can be improved.

The projecting portions of the light-transmissive member 12 can be formed by selecting an appropriate tool angle and an appropriate width of a dicing blade when the light-transmissive member is separated by dicing. The projecting portions may also be formed by using half-dicing as a method for dicing. By using such a method of forming the projecting portions, the light-transmissive member 12 having an integrated structure as a whole that includes a single wavelength conversion member as described below can be formed as shown in FIG. 5A.

In each of the light-transmissive member 12, the shape of the upper surface 12 a may be the same as, in other words, similar to, or may be different from the shape of the lower surface 12 b. For example, in the case where the lower surface 12 b has a square shape in a plan view, the upper surface 12 a may have a square, circular, elliptic, or fan shape. Regardless of whether the shapes of the upper surface 12 a and the lower surface 12 b are the same or different, the centers or the centroids of the shapes may or may not correspond to each other.

The upper surfaces 12 a of the plurality of light-transmissive members 12 may have the same shape, or some or all of the upper surfaces 12 a of the plurality of light-transmissive members 12 may have different shapes. The lower surfaces 12 b of the plurality of light-transmissive members 12 may have the same shape, or some or all of the lower surfaces 12 b of the plurality of light-transmissive members 12 may have different shapes. Whether the shapes are the same or different, all the upper surfaces 12 a preferably have the same area. This structure allows for effectively reducing unevenness in luminance.

The upper surfaces 12 a of the light-transmissive members 12 collectively constitute the light-emitting part of the light-emitting device. In other words, light emitted from the light-emitting elements is emitted only through the upper surfaces 12 a. Accordingly, in the light-emitting device, the upper surfaces of a plurality of light-transmissive members collectively constitute the light-emitting part. The outermost periphery of the light-emitting part can have various shapes in accordance with the shapes of the upper surfaces 12 a of the light-transmissive members. Among various shapes, the outermost periphery of the light-emitting part collectively constituted by the upper surfaces 12 a preferably has a square shape or a circular shape. For example, four light-transmissive members, each of which has a upper surface of a fan shape, and four light-emitting elements are arranged such that the four fan shapes are combined together to form a circular shape, so that a light-emitting part having a circular shape in a plan view can be obtained (see, FIG. 3). In a similar manner, four light-transmissive members, each of which has an upper surface of a square shape, and four light-emitting elements are arranged such that the four square shapes are combined together to form a square shape, so that a light-emitting part having a square shape in a plan view can be obtained (see, FIGS. 1A and 2A). Such shapes enable a plurality of emitting surfaces to be close to one another, which allows for improving the luminance of the light-emitting part, reducing the unevenness in luminance, and improving the external appearance of the light-transmissive members when viewed from the light-extracting surfaces.

For example, the light-transmissive members are preferably disposed at intervals of 0.2 mm or more. With intervals equal to or more than a certain value, light emitted from a specific light-emitting element and passing through the covering member 13 described below can be prevented from entering a light-transmissive member other than the light-transmissive member connected to the upper surface of the specific light-emitting element, so that mixing of emission colors can be prevented. The light-transmissive members are preferably arranged at larger intervals therebetween, but if intervals between the light-transmissive members are too large, the size of the light-emitting device needs to be increased.

Accordingly, the light-transmissive members are preferably arranged at an interval that allows for preventing mixing of emission colors.

The upper and lower surfaces 12 a and 12 b of the light-transmissive members 12 may each have irregularities but are preferably flat.

It is more preferable that the upper and lower surfaces 12 a and 12 b be parallel to each other. It is preferable that each of the light-transmissive members 12 be arranged corresponding to a respective one of the light-emitting elements 11.

The light-transmissive members 12 may contain a wavelength conversion substance. The wavelength conversion substance may constitute the light-transmissive members in the form of, for example, materials cut out of a phosphor ingot such as single crystal phosphors, polycrystalline phosphors, and a sintered body made of phosphorous powder.

The light-transmissive members 12 may further contain light-transmissive resin as a binding agent.

Examples of the wavelength conversion substance include substances that can be excited by light emitted from the light-emitting elements. Examples of wavelength conversion substances that can be excited by blue or ultraviolet light-emitting elements include cerium-activated yttrium-aluminum-garnet phosphors (YAG:Ce); cerium-activated lutetium-aluminum-garnet phosphors (LAG:Ce); europium- and/or chromium-activated nitrogen-containing calcium aluminosilicate phosphors (CaO—Al₂O₃—SiO₂); europium-activated silicate phosphors ((Sr,Ba)₂SiO₄); nitride phosphors such as β-SiAION phosphors. CASN phosphors, and SCASN phosphors; KSF phosphors (K₂SiF₆:Mn); sulfide phosphors; and quantum-dot phosphors. Combinations of such wavelength conversion substances and blue or ultraviolet light-emitting elements allows for manufacturing light-emitting devices configure to emit various colors, such as a light emitting device configured to emit white light.

The light-transmissive members 12 may be substantially free of wavelength conversion substance. In this case, light emitted from the light-emitting elements is directly transmitted without being subjected to wavelength conversion. For example, with the use of light-emitting elements that respectively emit red, blue, and green light, mixing these emission colors allows for emitting white light.

The light-transmissive members may also contain various fillers for the purpose of, for example, adjusting the viscosity.

Each of the light-transmissive members of any of the first to third embodiments described below may have a layered structure as long as the light-transmissive members are light-transmissive. For example, as in a light-transmissive member 42 shown in FIG. 5B, a layered structure in which a first layer 42A and a second layer 42B, which are plate-shaped bodies having different sizes and containing the same wavelength conversion substance, are layered may be employed. A thickness of the first layer 42A and a thickness of a second layer 42B may be different or the same. Alternatively, for example, as in a light-transmissive member 52 shown in FIG, 5C, a layered structure in which the first layer 52A and the second layer 52B that contain different wavelength conversion substances are layered may be employed; as in a light-transmissive member 62 shown in FIG. 5D, a layered structure in which the first layer 62A that contains a wavelength conversion substance and the second layer 62B that does not contain a wavelength conversion substance but contains a filler are layered may be employed; or a layered structure in which such layers are alternately layered may be employed. In the plurality of light-transmissive members of a single light-emitting device, one or more of the plurality of light-transmissive members may contain a wavelength conversion member with a composition (more specifically, type and/or amount) different from the others of the plurality of light-transmissive members. The plurality of light-transmissive members 12 may include the same number of first light-transmissive members and second light-transmissive members that contain a wavelength conversion member with compositions that are different between the first and the second light-transmissive members but are the same among the first light-transmissive members and among the second light-transmissive members. In particular, wavelength conversion members that provide different emission colors are preferably used.

A light-transmissive resin, glass, a ceramic, or the like can be used for a material of the light-transmissive resin. In particular, a light-transmissive resin is preferably used, and examples thereof include thermosetting resins such as silicone resins, modified silicone resins, epoxy resins, and phenolic resins, and thermoplastic resins such as polycarbonate resins, acrylic resins, methylpentene resin, and polynorbornene resin. A silicone resin, which has good resistance to light and heat, is particularly preferable.

The light-transmissive members 12 may be connected to the light-emitting elements 11 using a known method such as compression, sintering, and bonding with the use of an adhesive.

Covering Member 13

The covering member 13 integrally covers the lateral surfaces of the light-emitting elements 11 and the lateral surfaces of the light-transmissive members 12. In particular, the upper surface of the covering member 13 is preferably in the same plane with the upper surfaces 12 a of the light-transmissive members 12. The covering member 13 having such a structure can block light traveling toward the lateral surfaces of the light-emitting elements and the lateral surfaces of the light-transmissive members, which can prevent the light distribution from being broad, so that light with good visibility and high luminance can be obtained. Further, preventing the light distribution from being broad allows for, in the case where optical components such as lenses and reflectors are used, miniaturizing the optical components. The expression “good visibility” as used herein refers to that the boundary between the light-emitting portion and the non-light-emitting portion is clear.

The greater the difference in luminance between the light-emitting region and the non-light-emitting region is, the better the visibility is.

The plurality of electrodes are exposed from the covering member 13 at the lower surfaces of the light-emitting elements 11, and the covering member 13 preferably covers the lower surface of the layered structure constituting each of the light-emitting elements. With this structure, a portion of light traveling toward the lower surfaces of the light-emitting elements 11 can be reflected and extracted. In this case, a surface of the covering member 13 covering the lower surface of the layered structure is preferably in the same plane with a surface of each of the plurality of electrodes. This structure allows for reducing leakage of light from the light-emitting elements and thus allows for improving the light extraction efficiency.

The covering member 13 is preferably a resin member containing a themosetting resin such as a silicone resin, a modified silicone resin, an epoxy resin, or a phenolic resin as a main component, more preferably a light-reflective resin member. The “light-reflective resin” refers to a resin material that has a reflectance with respect to light emitted from the light-emitting elements of 70% or more. For example, a white resin is preferable. With a white resin, light that has reached the covering member is reflected toward the light-extracting surface of each of the light-emitting elements, so that the light extraction efficiency of the light-emitting device can be enhanced.

For example, a light-transmissive resin in which a light-reflective substance is dispersed can be used fir the light-reflective resin. For the light-reflective substance, titanium oxide, silicon oxide, zirconium oxide, potassium titanate, aluminum oxide, aluminum nitride, boron nitride, mullite, or the like is preferably used. A light-reflective substance in a form of particles, fibers, flakes, or the like can be used. In particular, with a fibrous light-reflective substance, an effect of reductant, the thermal expansion coefficient of the covering member can also be expected, and thus a fibrous light-reflective substance is preferably used.

An amount of light reflected, transmitted, etc., by the covering member 13 can be changed by changing the content of the light-reflective substance or the like and/or a thickness of the covering member. Accordingly, the content of the light-reflective substance or the like and/or a thickness of the covering member can be appropriately adjusted according to properties of the light-emitting device to be obtained. For example, the content of the light-reflective substance is preferably 30 wt % or more with respect to the total weight of the covering member. For example, a portion of the covering member constituting an outer portion of the light-emitting device has a thickness (indicated by M in FIG. 1B) in a range of 50 μm to 500 μm, and a portion of the covering member between light-emitting elements has a thickness (indicated by Q in FIG. 1B) in a range of 100 μm to 1000 μm. A portion of the covering member between upper surfaces of light-transmissive members 12 has a thickness (indicated by in FIG. 1B) has a thickness, for example, similar to Q, that is, in a range of 100 μm to 1000 μm.

The covering member 13 can be molded using, for example, an injection molding method, a potting method, a resin printing method, a transfer molding method, a compression molding method, or a stereoscopic printing method.

Also, for example, as shown in FIG. 6, when the light-emitting device 10 (or the light-emitting device 20 or 30) is, mounted on a mounting, board 16, a resist 15 having a color that is the same as or similar to the color of a wavelength conversion member contained in the light-transmissive members 12 may be disposed using a stereoscopic printing method on a region of the surface of the covering member 13 surrounding the light-transmissive members 12 in a plan view of the light-emitting device, which allows the boundaries between the covering member 13 and the light-transmissive members 12 to be less noticeable. At this time, a surface of another electronic component 17 mounted on the mounting board 16 and a surface of the mounting board 16 may be integrally covered with the resist 15

Metal Layer

The light-emitting device preferably includes a plurality of metal layers 14 that cover a surface of the covering member 13 at a side opposite to the light-extracting surface of each of the light-emitting elements 11, in other words, at the lower surface side, and that are connected to the plurality of electrodes. For example, it is preferable that the plurality of metal layers 14 include a first metal layer 14 a and a second metal layer 14 b, and electrodes of the plurality of light-emitting elements with one polarity are connected to the first metal layer 14 a, and electrodes of the plurality of light-emitting elements with the other polarity are connected to a second metal layer 14 b. The first metal layer 14 a and the second metal layer 14 b are connected to the electrodes of the light-emitting elements and thus can function as external connecting terminals of the light-emitting device. The first metal layer 14 a and/or the second metal layer 14 b can also function as alignment parts for alignment with reference to the sizes, shapes, and positions at which they are formed.

Each of the plurality of metal layers 14 preferably has a size equal to or larger than the area of corresponding ones of the electrodes of the light-emitting elements 11. The first metal layer 14 a and the second metal layer 14 b preferably have substantially the same size and the same shape. For example, the first metal layer 14 a and the second metal layer 14 b can have a shape of a polygon such as triangles, pentagons, hexaaons, or quadrilaterals such as squares and rectangles, a shape formed by cutting off a portion of such a polygon, or a shape formed by rounding off a portion of such a polygon.

It is preferable that a shape of the first metal layer 14 a and a shape of the second metal layer 14 b are bilaterally symmetrical. One of the first metal layer 14 a and the second metal layer 14 b may include a portion that is cut off to indicate the polarity. Various shapes can be employed in accordance with the shape of the electrodes of the light-emitting elements.

A distance between the first metal layer 14 a and the second metal layer 14 b is preferably large enough to prevent short circuits due to spread of bonding members such as solder when the metal layer is bonded to a circuit board or the like on which the light-emitting device is to be mounted. The distance between the first metal layer 14 a and the second metal layer 14 b is preferably 20 μm or more, more preferably 50 μm or more.

The metal layer is preferably made of a material having good corrosion resistance and oxidation resistance than those of the electrodes. For example, the outermost layer of the metal layer is preferably made of a platinum-group metal such as Au or Pt. In the case where the mend layer covers a surface of the light-emitting device to be soldered, Au, which has good solderability, is preferably used for the outermost surface of the metal layer. The metal layer may be constituted by only one layer made of a single material, or may have a layered structure in which layers of different materials are layered. In particular, a metal material having a high melting point is preferably used for the metal layer, and examples of such a metal material include Ru, Mo, and Ta. Also, such a metal having a high melting point disposed between the outermost layer and the electrodes of the light-emitting elements can serve as a diffusion preventing layer that can reduce diffusion of Sn contained in a solder into the electrodes and layers near the electrodes. Examples of a layered structure of the metal layer including such a diffusion preventing layer include Ni/Ru/Au and Ti/Pt/Au. The diffusion preventing layer (such as Ru) has a thickness, for example, in a range of 1 nm to 100 nm.

The metal layer can have any appropriate thickness. The metal layer can have a thickness that allows for selectively occurring laser ablation and is, for example, preferably 1 μm or less, more preferably 100 nm or less. Further, the metal layer preferably has a thickness of the metal layer that allows for reducing corrosion of the electrodes, such as 5 nm or more. In the case where a plurality of layers constitute the metal layer, the thickness of the metal layer as used herein refers to the total thickness of the layers.

The metal layer may include one first metal layer 14 a and one second metal layer 14 b, or, for example, at least two first metal layers 14 a separate from each other may be disposed on both sides of the second metal layer 14 b (for example, as in the arrangement of the electrodes 11 a and 11 b as shown in FIG. 1C).

Alternatively, two or more first metal layers 14 a and two or more second metal layers 14 b may be alternately disposed (for example, as in the arrangement of the electrodes 11 a and 11 b as shown in FIG. 4A). The shapes, sizes, and the like are preferably changed as appropriate in accordance with the arrangement of the electrodes 11 a and 11 b and the like as shown in FIG. 4B.

The metal layer can be formed by sputtering, vacuum evaporation, atomic layer deposition (ALD), metal organic chemical vapor deposition (MOCVD), plasma-enhanced chemical vapor deposition (PECVD), atmospheric-pressure plasma-enhanced chemical vapor deposition, plating, or the like.

Protective Element

The light-emitting device may include a protective element in addition to the light-emitting elements 11. With the protective element, the light-emitting device can be protected against breakdowns of the light emitting elements and degradation of performance due to application of excessive voltages. For the protective element, any appropriate protective element may be used, and any known element may be used. The protective element is preferably embedded in the covering member 13.

First Embodiment

The light-emitting device 10 according to a first embodiment includes the light-emitting elements 11, the light-transmissive members 12, and the covering member 13 as shown in FIG. 1A to FIG. 1E.

Each of the light-emitting elements 11 has a layered structure including a semiconductor layer, the plurality of electrodes 11 a and 11 b connected to a surface of the layered structure. Further, an upper surface of each of the light-emitting elements 11, that is, a surface of each of the light-emitting elements 11 on which the plurality of electrodes 11 a and 11 b are not disposed, serves as a light-extracting surface. In the present embodiment, four square-shaped light-emitting elements 11 are arranged in two rows and two columns. The distance (indicated by Q in FIG. 1B) between the light-emitting elements in this case is 600 μm.

Each of the light-transmissive members 12 has a lower surface 12 b has a square shape and facing the light-extracting surface of the light-emitting element 11, and a square upper surface 12 a opposite to the lower surface 12 b. The upper surface 12 a and the lower surface 12 b are parallel to each other, and the centers of the upper and lower surfaces 12 a and 12 b coincide with each other. A single light-transmissive member 12 is disposed with respect to each of the light-emitting elements 11. In the present embodiment, four light-transmissive members 12 each having a square shape are disposed.

The periphery of the upper surface 12 a of each light-transmissive member 12 coincides with the outer periphery of the corresponding light-emitting element 11 in a plan view.

The light-transmissive member 12 contains a wavelength conversion substance and a light-transmissive resin, such as a silicone resin. For example, in two of the plurality of light-transmissive members (first light-transmissive members) vertically or laterally aligned, the wavelength conversion substance is a yellow or red phosphor, the content of which is 30% to 80% of the total weight of the light-transmissive member 12 and in other two of the plurality of light-transmissive members (second light-transmissive members) vertically or laterally aligned, the wavelength conversion substance is to yellow phosphor, the content of which is 0.01% to 80% of the total weight of the light-transmissive member 12. In this structure, white light emitted from the first light-transmissive members has a color temperature lower than the color temperature of white light emitted from the second light-transmissive members.

In each of the light-transmissive members 12, the upper surface 12 a has an area smaller than an area of the lower surface 12 b as shown in FIG. 18. In the present embodiment, the upper surface 12 a has an area approximately 20% smaller than an area of the lower surface 12 b. To achieve such a difference in area, the light-transmissive member 12 has the projecting portions Z laterally protruding from the lateral surfaces as shown in FIG. 1B and FIG. 5A. A length of the projecting portions Z is, for example, in a range of 20 μm to 100 μm. Each of the projecting portions Z has a perpendicular surface perpendicular to the lower surface 12 b and in contact with the lower surface 12 b, and a surface in contact with the perpendicular surface, and parallel to the upper surface 12 a of the light-transmissive member 12. The distance between the projecting portions Z of adjacent light-transmissive members 12 (indicated by S in FIG. 1B) is 500 μm.

The upper surfaces 12 a of the light-transmissive members 12 constitutes the light-emitting portion as shown in FIG. 1A, and the outermost periphery of the light-emitting portion (X1 in FIG. 1A) has a square shape.

The covering member 13 integrally covers the lateral surfaces of the light-emitting elements 11 and the lateral surfaces of the light-transmissive members 12. The covering member 13 is also disposed on the surface on which the pairs of electrodes 11 a and 11 b of the light-emitting elements 11 are disposed so as not to cover the plurality of electrodes 11 a and 11 b. The upper surface of the covering member 13 is in the same plane with the upper surfaces 12 a of the light-transmissive members 12. The lower surface of the covering member 13 is in the same plane with the lower surfaces of the electrodes 11 a and 11 b.

The covering member 13 contains a light-reflective substance and a light-transmissive resin. The light-transmissive resin is a silicone resin, and the light reflective substance is titanium oxide. The content of titanium oxide is 40% of the total weight of the covering member 13.

In the present embodiment, a portion of the covering member 13 between the light emitting elements 11 has a thickness Q of 600 μm, and a portion of the covering member 13 at an outside of the light emitting elements 11 has a thickness M of 150 μm.

As shown in FIGS. 1C and 1E, the light-emitting device 10 includes the first metal layers 14 a and the second metal layer 14 b in a plan view, which are a plurality of metal layers covering a surface of the covering member 13 at a lower side of the light-emitting elements 11, being connected to the plurality of electrodes 11 a and 11 b, and functioning as external terminals. For example, in a plan view, two separated first metal layers 14 a are disposed on both sides of the light-emitting device 10 such that the second metal layer 14 b is disposed therebetween. The first metal layers 14 a and the second metal layer 14 b are arranged with a distance therebetween that allows for preventing short circuits due to spread of bonding members such as solder when the metal layer is bonded to a circuit board or the like on which the light-emitting device is to be mounted. For example, a distance between the first metal layers 14 a and the second metal layer 14 b is 30 μm. Each of the first metal layers 14 and the second metal layer 14 b is connected to a corresponding one of the electrodes 11 a or 11 b of the light-emitting elements 11. In the present embodiment, the first metal layers 14 a and the second metal layer 14 b have approximately the same size, are disposed along a side of the light-emitting device 10, and each have a rectangular shape in a plan view.

Each of the first metal layers 14 a and the second metal layer 14 b has a layered structure of Ni/Ru/Au from the electrodes 11 a and 11 b side of the light-emitting elements 11, and have a total thickness of 500 Å.

In the light-emitting device including a plurality of light-emitting elements, in the case where two of the four light-transmissive members serve as the first light-transmissive members and the other two serve as the second light-transmissive members as described above, the structure in which the first light-transmissive members and the second light-transmissive members contains wavelength conversion substances with compositions different between the first and second light-transmissive members and the upper surfaces of the first light-transmissive members and the upper surfaces of the second light-transmissive members constitutes the light-emitting part having the periphery X1 with a square shape allows for effectively reducing unevenness in luminance attributable to gaps between the light-emitting elements and improving luminance. The external appearance of the light-emitting device viewed from the light-extracting surface can be also improved.

Second Embodiment

In a light-emitting device 20 according to a second embodiment, each of light-transmissive members 22 has a square shape in a plan view, and also has an upper surface 22 a and a lower surface 22 b having square shapes in a plan view. The difference between an area of the upper surface 22 a and the lower surface 22 b similar to that in each of the light-transmissive members in the first embodiment. As shown in FIGS. 2A and 2B, the center of the upper surface 22 a is shifted from the center of the lower surface 22 b, and two sides of the square upper surface 22 a overlap two sides of the lower surface 22 b. Accordingly, projecting portions Z2 are disposed substantially along two sides of the light-transmissive member 22 in as plan view.

The light-transmissive members 22 are disposed such that the two sides of the upper surface 22 a of each of the light-transmissive members 22 that coincide with two sides of the lower surface 22 b thereof face the center of the light-emitting device 20 in a top view. A distance R between the light-emitting elements 11 in this case is 100 μm.

Accordingly, although the areas of the light-extracting surfaces of the light-emitting elements 11 are the same as those in the first embodiment, the area of the light-emitting part surrounded by a periphery X2 can be reduced, so that the luminance can be further improved and unevenness in luminance can be prevented.

Other configurations in the second embodiment is substantially the same as those of the light-emitting device 10 according to the first embodiment, and substantially the same effects can be obtained.

Third Embodiment

In a light-emitting device 30 according to a third embodiment, each of light-transmissive members 32 has a square shape in a plan view, and has a lower surface 32 b having a square shape and an upper surface 32 a having a fan shape in a plan view as shown in FIG. 3. The difference in area between the upper and lower surfaces 32 a and 32 b of each of the light-transmissive members 32 is similar to that in each of the light-transmissive members 12 according to the first embodiment, and the two adjacent straight sides of the fan-shaped upper surface 32 a overlap two of the sides of the lower surface 32 b. Thus, a projecting portion is located at a region substantially other than the two sides of the light-transmissive member 32 in a plan view.

Each of the light-transmissive members 32 is disposed such that the two straight sides of the upper surface 32 a and two sides of the lower surface 32 b that coincide with the two straight sides of the upper surface 32 a in a plan view face the center of the light-emitting device 30. The distance between the light-emitting elements 11 in this structure is 100 μm.

Accordingly, in a plan view, an outermost periphery X3 of the light-emitting portions has a circular shape, and each of the light-emitting portions has an area a little smaller than the area of the light-extracting surface of a respective one of the light emitting elements 11. This allows for further improving luminance and reducing unevenness in luminance.

Other configurations of the light emitting device 30 is substantially the same as the structure of the light-emitting device 10 and 20 according to the first and second embodiment, respectively, and substantially the same effects can be obtained. 

What is claimed is:
 1. A light-emitting device comprising: a plurality of light-emitting elements each having a light-extracting surface, the light-emitting elements each including a layered structure including a semiconductor layer, and a plurality of electrodes connected to the layered structure; a plurality of light-transmissive members each having a lower surface facing the light-extracting surface of at least one of the light-emitting elements, and an upper surface opposite to the lower surface and having an area smaller than an area of the lower surface, the upper surface of each of the light transmissive members collectively constituting a light-emitting part having an outermost periphery with a square shape or a circular shape; and a covering member integrally covering lateral surfaces of the light-emitting elements and lateral surfaces of the light-transmissive members.
 2. The light-emitting device according to claim 1, wherein each of the light-transmissive members is disposed with respect to a respective one of the light-emitting elements.
 3. The light-emitting device according to claim 1, wherein the upper surface of one of the light-transmissive members has a fan shape.
 4. The light-emitting device according to claim 1, wherein at least one of the light-transmissive members contains a wavelength conversion substance.
 5. The light-emitting device according to claim 1, wherein the light-transmissive members include a first light-transmissive member and a second light-transmissive member, and, the fast light-transmissive member contains a first wavelength conversion substance and the second light-transmissive member contains a second wavelength conversion substance having a different composition from the first wavelength conversion substance.
 6. The light-emitting device according to claim 5, wherein an area of an upper surface of the first light-transmissive member is the same as an area of an upper surface of the second light-transmissive member.
 7. The light-emitting device according to claim 1, wherein at least one of the light-transmissive members is substantially free of wavelength conversion substance.
 8. The light-emitting device according to claim 1, further comprising; a first metal layer; and a second metal layer, wherein the first metal layer and the second metal layer cover a surface of the covering member opposite to the light emitting part, and the first metal layer and the second metal layer are connected to the electrodes of the light-emitting elements.
 9. The light-emitting device according to claim 8, further comprising an additional first metal layer spaced apart from the first metal layer so that the second metal layer is disposed between the first metal layer and the additional first metal layer.
 10. The light-emitting device according to claim 1, wherein each of the light-transmissive members has a projecting portion laterally protruding from at least one of the lateral surfaces of a corresponding one of the light-transmissive members, the projecting portion having a perpendicular surface perpendicular to the lower surface of the corresponding one of the light-transmissive members and in contact with the lower surface, and a surface in contact with the perpendicular surface and parallel to the upper surface of the corresponding one at the light-transmissive members.
 11. The light-emitting device according to claim 1, wherein the upper surface of each of the light-transmissive members is substantially flush with an upper surface of the covering member.
 12. The light-emitting device according to claim 1, wherein at last a part of an edge of the upper surface of each of the light-transmissive members coincides with at least a part of a periphery of a corresponding one of the light-emitting elements in a plan view.
 13. The light-emitting device according to claim 1, wherein at least a part of an edge of the lower surface of each of the light-transmissive members coincides with at least a part of a periphery of a corresponding one of the light-emitting elements in a plan view.
 14. The light-emitting device according to claim 1, wherein the covering member contains a light-reflective substance. 